Monga, Celestin, author
Lynne Rienner, 1996
Buku Teks
Edie, Carlene J., author
Wadsworth/Thomson Learning, 2003
Buku Teks
Esacove, Anne, author
Oxford University Press, 2016
eBooks
Wiedner, Donald L. Donal Lawrence)
Random House, 1962
Buku Teks
Cambridge University Press, 2012
eBooks